Toss it. But save the rice you packed it in. Truffles have a useful life of only a couple of weeks or so unless they are somehow preserved. I would hate to throw away a thing as valuable as a white truffle but the thing is, if you own one, use it lavishly and right away.

Pierino, I think you're right. Even if it's stored in the freezer, it would still need to be used within a certain time frame, right? I would love to hear more about the rice though and what you would do with it though.